"Don't tell me it doesn't work. Torture works, OK folks?" the brash billionaire told a crowd in South Carolina, site of the next Republican primary on Saturday.

Trump has repeatedly advocated enhanced interrogation techniques for foreign prisoners, and he said again he would "absolutely" allow waterboarding, which simulates the feeling of drowning.

"But we should go much stronger than waterboarding," he said. "That's the way I feel. They're chopping off heads. Believe me, we should go much stronger because our country's in trouble, we're in danger. We have people that want to do really bad things."

Waterboarding was practiced until late in the George W. Bush administration but was disavowed by President Barack Obama. A 2014 Senate Intelligence Committee report concluded that harsh interrogation techniques failed to produce information the CIA couldn't have obtained elsewhere or didn't already have.

Trump's comments could further alarm some Republican leaders, who fear Trump or Texas Sen. Ted Cruz will collect the delegates needed to secure the party's nomination before a more mainstream candidate can consolidate voters' support.

So-called establishment Republicans worry that Trump or Cruz could jeopardize the party's chances of winning in November's general election.

Candidates Jeb Bush, John Kasich and Marco Rubio are jostling to be that more mainstream candidate, or at least keep their campaigns afloat if they don't.

Rubio yesterday said going forward he'll address audience members who use "outrageous, over-the-top and egregious" language during his events. That's in response to an incident last night when an audience member shouted out "Waterboard Hillary!" Rubio laughed at the time.